1. Field of the Invention
The present invention pertains to medical instruments and devices. In particular, it pertains to measuring apparatus for determining the size of vessels and prosthetic grafts for the replacement of damaged or diseased vessel sections.
2. Description of the Prior Art
Frequently, in cardiovascular surgery, it is necessary to remove or bypass a section of a blood vessel for replacement or circumvention by a prosthetic graft. Depending on what section is removed or bypassed, the graft may be straight or bifurcated, having an aorta and, normally, two limbs. To determine the size graft needed for replacement, the vessel section being replaced or dissected should be measured, preferably before the vessel is severed or dissected. If this is not done, selection of the proper graft size may be by trial and error, consuming valuable surgery time. Furthermore, if the graft selected first is not the proper size, it becomes contaminated and must be resterilized before subsequent use. If contaminated by blood it must be discarded. Due to the materials therefor, grafts can only be resterilized a few times before they are permanently damaged and will have to be thrown away. Since they are expensive, this is a waste of money as well as time.
Quite frequently, grafts may be removed from their packages losing size identification. For this reason, a measuring device is also desirable to determine the graft size.
One problem associated with determining the size of a vessel, while still in the body, is the ability to measure within a body cavity. Sometimes these body cavities may be extremely deep, rendering certain types of instruments unusable.
There are few instruments available for measuring vessels and grafts. One which is available is of the caliper type, having a fixed point and a movable point on a movable caliper arm which, as the caliper arm moves, are positioned so that the points engage the vessel on opposite sides thereof. However, since vessels are generally very flexible, there is a distinct possibility that an inaccurate measurement may be taken by placing too much pressure on the caliper arm. In addition, vessels are not always disposed in the body for access by a caliper type device. An example of a caliper type measuring instrument may be seen in U.S. Pat. No. 3,740,779.
Some flat sheet type gauges have been used in the past for internal measurement of vessels and grafts. Of course, with such a measuring device, the vessel cannot be measured until it is severed from the body. As already pointed out, this may result in the loss of valuable surgical time. Furthermore, such a means of measuring a flexible vessel of graft can be improperly forced into the vessel or graft interior, causing the tubular structure to be elongated, accommodating the wrong size and maybe resulting in the selection of an improperly sized graft.
There is a long felt need for a suitable measuring instrument in cardiovascular surgery. The fact that none of those presently used has found wide acceptance, indicates that improvements in this area are awaited.